1. Field of the Invention
The present invention relates to an image encoding device, and an image encoding method, and more specifically, it relates to an image encoding device, and an image encoding method, whereby deterioration in image quality can be reduced even when repeating encoding and decoding of an image by employing a long GOP configuration.
2. Description of the Related Art
Hitherto, with an image encoding method such as MPEG2 (Moving Picture Experts Group 2) or the like, it is a great problem to maintain subjective image quality to ideally distribute a code amount.
For example, an ideal code amount distribution of a still image is a state in which distortion is uniformly encoded (with a fixed quantized scale). When reaching a code amount whereby this distortion becomes great, subjective image quality can be enhanced by biasing the distortion toward a high-frequency component or complicated portion.
Now, for example, with International Publication WO96/28937, an image signal encoding method has been disclosed wherein the image quality of a decoded image can be improved by employing code amount control according to a feed forward method to enable control adapted to the local property of an image quality signal. The feed forward method is for determining a suitable quantizing scale in a range where a generated code amount does not exceed a target generated code amount by calculating a code amount to be generated in increments of equal lengthening regarding a plurality of quantizing scales.
On the other hand, with code amount control such as TM5 proposed as a test model with MPEG2, or the like, code amount control is performed by performing feedback control using relationship between the remaining amount of a virtual buffer, a quantization index at the time of previous encoding, and a generated code amount.
Also, in order to suppress deterioration in image quality at the time of repeating encoding and decoding of an image, for example, with International Publication WO2009/035144, the quantizing parameter and quantizing matrix used at the last encoding are detected.